Method for connecting at least one turbine blade to a turbine disk or a turbine ring

ABSTRACT

The invention relates to a method for connecting at least one turbine blade ( 10 ) to a turbine disk ( 18 ) or a turbine ring for a turbine stage of a turbomachine, particularly a thermal gas turbine, wherein first a connecting body ( 16 ) is formed on the at least one turbine blade ( 10 ) by means of a cold gas spraying method, and the connecting body ( 16 ) is subsequently connected to turbine disk ( 18 ) or to the turbine ring by means of a fusion-welding method. The invention further relates to a turbine stage for a turbine of a turbomachine as well as a turbomachine having a turbine.

The invention relates to a method for connecting at least one turbine blade to a turbine disk or a turbine ring for a turbine stage of a turbomachine, in particular a thermal gas turbine. The invention further relates to a turbine stage of the type indicated in the preamble of patent claim 4 for a turbine of a turbomachine as well as a turbomachine of the type indicated in the preamble of patent claim 6.

This type of method for connecting at least one turbine blade to a turbine disk or a turbine ring as well as this type of turbine stage, which comprises a turbine disk or a turbine ring that is connected to one or more turbine blades at least indirectly, are known from the prior art. For its part, the turbine stage is arranged in a single-stage or multi-stage turbine of a turbomachine, particularly constructed as a thermal gas turbine. Advances in gas turbine construction, however, set continually higher requirements for the materials used. The turbine blades serving as rotating blades or vanes are thus essentially produced as polycrystalline, monocrystalline or directionally solidified cast parts made of high-temperature-resistant base alloys. Turbine blades that are produced from composite materials that perform well at high temperatures are also known.

This configuration, however, leads to the fact that the turbine blades cannot be fusion welded or can be fusion welded only with great difficulty. A connection to a turbine disk or a corresponding turbine ring that can be fusion welded and that can be produced from a nickel base alloy is thus not possible via conventional fusion welding methods and leads to considerable increased cost. Alternatively, friction welding or diffusion welding methods are known for at least an indirect connection between turbine blade and turbine disk or turbine ring, but these methods require a high equipment expense. In addition, temperatures that are incompatible for the usual base alloys may occur with these welding methods.

The problem of the present invention is thus to create a method of the type named initially, which can be conducted in a cost-effective and flexible manner. Another problem of the invention is to provide a corresponding turbine stage having a turbine disk or a turbine ring and at least one turbine blade, which can be produced in a cost-effective and flexible manner.

The problem is solved according to the invention by a method according to patent claim 1, a turbine stage with the features of patent claim 4 as well as by a turbomachine with the features of patent claim 6. Advantageous embodiments with appropriate and non-trivial enhancements of the invention are indicated in the respective dependent claims, wherein advantageous configurations of the method are also to be viewed—insofar as they are applicable—as advantageous configurations of the turbine stage, and vice versa.

In a method according to the invention for connecting at least one turbine blade to a turbine disk or a turbine ring for a turbine stage of a turbomachine, in particular a thermal gas turbine, first a connecting body is formed on at least one turbine blade by means of a cold gas spraying method, and the connecting body is subsequently connected to the turbine disk or the turbine ring by means of a fusion welding method. A coating method in which the material in powder form for the later connecting body is introduced onto the turbine blade at a high speed is called a cold gas spraying method. It may be provided for this purpose that a gas heated to a comparatively low temperature is accelerated to supersonic speed by expansion in a nozzle (so-called Laval nozzle). Subsequently, the powder particles are introduced into this gas and in this way are accelerated to such high velocities that they form a solidly adhering layer with a high density and compactness without fusing upon impact on the turbine blade. The cold gas spraying method is preferably conducted in such a way that the kinetic energy of the powder particles is insufficient for a complete fusion at the time point of the impact. In this way, a minimum input of heat into the turbine blade serving as the substrate is simultaneously assured. The impact velocity of the powder particles can be adjusted in a targeted manner as a function of the material used, for example, by means of an optimized nozzle design, changes in gas temperature, higher gas pressure or changes in particle size. Since the material of the connecting body formed in this way is not fused, an oxidation of the involved materials is reliably prevented. Subsequently, the turbine blade is connected indirectly to the turbine disk or the turbine ring via the connecting body by means of the fusion welding method. Basically, as the material of the connecting body, all materials can thus be used that can be plastically deformed, can be fusion welded and can withstand the later loads during operation in an assigned turbomachine. The method according to the invention can thus be conducted in a considerably cost-effective manner without high equipment expense. Since the connection between the turbine blade and the turbine disk or the turbine ring is effected by means of the connecting body, the material and the geometry of the turbine blade are of secondary importance, for which reason the method can be carried out in a particularly flexible manner. It may thus be basically provided that the connecting body can be formed of multiple parts.

In an advantageous embodiment of the invention, it is provided that the connecting body is machined, particularly precision-machined, prior to the fusion welding method. Precision-machined is to be understood here preferably as a machining by cutting, whereupon both a desired surface quality as well as a required dimensional stability of the connecting body can be assured in a simple and cost-effective manner.

Further advantages result if the connecting body is formed in the region of a blade foot of the turbine blade and/or as a blade foot of the turbine blade. In this way, a simple and mechanically stable connection of the turbine blade to the turbine disk or the turbine ring is made possible via the connecting body.

In another advantageous embodiment of the invention, it is provided that the connecting body is formed as a function of the geometry of the turbine blade and/or of the turbine disk or of the turbine ring. The method can be used here in a particularly flexible manner for producing different turbine stages.

In another embodiment, it has been shown to be advantageous, if an electron-beam welding method and/or a laser welding method and/or an inductive high-frequency pressure welding method and/or an inductive low-frequency pressure welding method is used as the fusion welding method. In this way, high welding speeds with extremely deep and narrow welds are possible with short thermal delay.

Since several turbine blades are connected to the turbine disk or the turbine ring via respective connecting bodies, a complete turbine stage for a turbomachine can be produced with the advantages according to the invention and particularly with reduced costs and an increased flexibility.

Another aspect of the invention relates to a turbine stage for a turbine of a turbomachine, wherein the turbine stage can be produced in a cost-effective and flexible manner by connecting at least one turbine blade to the turbine disk or the turbine ring via a connecting body which has been formed on the turbine blade by means of a cold gas spraying method. Additional advantages that result can be taken from the preceding descriptions.

Since the connecting body is connected to the turbine disk or the turbine ring by means of a fusion welding method, the manufacturing costs of the turbine stage can be additionally reduced.

In another advantageous embodiment of the invention, it is provided that the turbine disk or the turbine ring and/or the turbine blade is manufactured from a nickel base alloy and/or a cobalt base alloy and/or a titanium aluminide and/or a metal-matrix composite material and/or a ceramic-matrix composite material. In this way, the turbine stage reliably possesses the required mechanical and thermal properties for later use in an assigned turbomachine and also can be adapted in a particularly flexible manner to the specific requirement profile.

Another aspect of the invention relates to a turbomachine, in particular a thermal gas turbine, with a turbine that comprises a turbine stage having a turbine disk or a turbine ring that is connected to at least one turbine blade, at least indirectly, wherein it is provided according to the invention that the turbine disk or the turbine ring and the at least one turbine blade of the turbine stage are connected to one another by means of a method according to one of the preceding examples of embodiment, or that the turbine stage is formed according to one of the preceding embodiment examples. The combinations of features resulting from this and their advantages can be taken from the corresponding descriptions.

Further advantages, features and particulars of the invention result based on the following description of an example of embodiment and based on the drawings. Here:

FIG. 1 shows a perspective frontal view of a turbine blade;

FIG. 2 shows a perspective oblique view of a connecting body formed on a blade foot of the turbine blade shown in FIG. 1; and

FIG. 3 shows a cut-away and perspective frontal view of a turbine disk, which is connected to the turbine blade via the connecting body.

FIG. 1 shows a perspective frontal view of a turbine blade 10, the general construction of which is known from the prior art. Turbine blade 10, which is manufactured as a cast part from a high-temperature-resistant nickel base alloy, comprises a radial outer shroud 12 and a radial inner blade foot 14. Since the material from which turbine blade 10 is manufactured cannot be fusion welded or can be fusion welded only with great difficulty, a connecting body 16 shown in perspective oblique view in FIG. 2 is formed by means of a cold gas spraying method in the region of blade foot 14 of turbine blade 10. The connecting body 16, which is formed from a plastically deformable material that can be fusion welded, makes it possible in a subsequent step to connect turbine blade 10 to a turbine disk 18 via a cost-effective fusion-welding method. Basically, instead of turbine disk 18, a turbine ring (not shown) may be provided, wherein both turbine disk 18 as well as the turbine ring can be formed of one part or of several parts. In addition, it may be provided that connecting body 16 forms blade foot 14. Likewise, it can be basically provided that connecting body 16 is or will be formed of several parts or several pieces, so that the connection between turbine blade 10 and turbine disk 18 is produced indirectly via several connecting body parts (not shown).

FIG. 3 shows a cut-away and perspective frontal view of turbine disk 18, which is connected in the region labeled with arrow III to turbine blade 10 via connecting body 16 presently formed in one piece. For example, an electron-beam welding method, a laser welding method, an inductive high-frequency pressure welding method and/or an inductive low-frequency pressure welding method can be used as the fusion-welding method. Basically, however, other welding methods familiar to the person skilled in the art also can be provided. In addition, it can be provided that connecting body 16 is precision-machined prior to fusion welding, whereby a simple geometric fitting between turbine blade 10 and turbine disk 18 is made possible. A complete turbine stage for a turbine of a thermal gas turbine can be produced by connecting several turbine blades 10 in an analogous way to turbine disk 18. In this way, it can be basically provided that the method is also used for the production of compressor stages for a compressor of a turbomachine or for connecting compressor blades to a compressor disk. 

1. A method for connecting at least one turbine blade (10) that cannot be fusion welded or can be fusion welded only with great difficulty to a turbine disk (18) that can be fusion welded or a turbine ring that can be fusion welded for a turbine stage of a turbomachine, particularly a thermal gas turbine, in which a geometrically defined connecting body (16) is first formed on the at least one turbine blade (10) by means of a cold gas spraying method and the connecting body (16) is subsequently connected to turbine disk (18) or to the turbine ring by means of a fusion-welding method, wherein connecting body (16) is formed in the region of a blade foot (14) of turbine blade (10) and/or as a blade foot (14) of turbine blade (10) as a function of the geometry of turbine blade (10) and/or of turbine disk (18) or of the turbine ring and is precision-machined prior to the fusion-welding method.
 2. The method according to claim 1, further characterized in that an electron-beam welding method and/or a laser welding method and/or an inductive high-frequency welding method and/or an inductive low-frequency welding method is used.
 3. The method according to claim 1, further characterized in that several turbine blades (10) are connected to turbine disk (18) or to the turbine ring via respective connecting bodies (16).
 4. A turbine stage for a turbine of a turbomachine, particularly a thermal gas turbine having a turbine disk (18) or a turbine ring, which is connected to at least one turbine blade (10) at least indirectly, is hereby characterized in that the at least one turbine blade (10) is connected to turbine disk (18) or to the turbine ring via a geometrically defined connecting body (16) formed on turbine blade (10) by means of a cold gas spraying method, wherein connecting body (16) is formed in the region of a blade foot (14) of turbine blade (10) and/or as a blade foot (14) of turbine blade (10) as a function of the geometry of turbine blade (10) and/or of turbine disk (18) or of the turbine ring, is precision-machined for its connection to turbine disk (18) or to the turbine ring and is connected to turbine disk (18) or to the turbine ring by means of a fusion-welding method.
 5. The turbine stage according to claim 4, further characterized in that turbine disk (18) or the turbine ring and/or turbine blade (10) is manufactured from a nickel base alloy and/or a cobalt base alloy and/or a titanium aluminide and/or a metal-matrix composite material and/or a ceramic-matrix composite material.
 6. A turbomachine, particularly a thermal gas turbine, with a turbine that comprises a turbine stage having a turbine disk (18) or a turbine ring that is connected to at least one turbine blade (10) at least indirectly, is hereby characterized in that turbine disk (18) or the turbine ring and the at least one turbine blade (10) of the turbine stage are connected to one another by means of a method according to claim 1 and/or that the turbine stage is formed according to one of claims
 4. 